linux-kernel - [for-next][PATCH 06/21] trigger_next should increase position index

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-Id: <20200130144811.117984529@goodmis.org>
Date:   Thu, 30 Jan 2020 09:47:49 -0500
From:   Steven Rostedt <rostedt@...dmis.org>
To:     linux-kernel@...r.kernel.org
Cc:     Ingo Molnar <mingo@...nel.org>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Vasily Averin <vvs@...tuozzo.com>
Subject: [for-next][PATCH 06/21] trigger_next should increase position index

From: Vasily Averin <vvs@...tuozzo.com>

if seq_file .next fuction does not change position index,
read after some lseek can generate unexpected output.

Without patch:
 # dd bs=30 skip=1 if=/sys/kernel/tracing/events/sched/sched_switch/trigger
 dd: /sys/kernel/tracing/events/sched/sched_switch/trigger: cannot skip to specified offset
 n traceoff snapshot stacktrace enable_event disable_event enable_hist disable_hist hist
 # Available triggers:
 # traceon traceoff snapshot stacktrace enable_event disable_event enable_hist disable_hist hist
 6+1 records in
 6+1 records out
 206 bytes copied, 0.00027916 s, 738 kB/s

Notice the printing of "# Available triggers:..." after the line.

With the patch:
 # dd bs=30 skip=1 if=/sys/kernel/tracing/events/sched/sched_switch/trigger
 dd: /sys/kernel/tracing/events/sched/sched_switch/trigger: cannot skip to specified offset
 n traceoff snapshot stacktrace enable_event disable_event enable_hist disable_hist hist
 2+1 records in
 2+1 records out
 88 bytes copied, 0.000526867 s, 167 kB/s

It only prints the end of the file, and does not restart.

Link: http://lkml.kernel.org/r/3c35ee24-dd3a-8119-9c19-552ed253388a@virtuozzo.com

https://bugzilla.kernel.org/show_bug.cgi?id=206283
Signed-off-by: Vasily Averin <vvs@...tuozzo.com>
Signed-off-by: Steven Rostedt (VMware) <rostedt@...dmis.org>
---
 kernel/trace/trace_events_trigger.c | 5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

diff --git a/kernel/trace/trace_events_trigger.c b/kernel/trace/trace_events_trigger.c
index 60959c31791d..dd34a1b46a86 100644
--- a/kernel/trace/trace_events_trigger.c
+++ b/kernel/trace/trace_events_trigger.c
@@ -116,9 +116,10 @@ static void *trigger_next(struct seq_file *m, void *t, loff_t *pos)
 {
 	struct trace_event_file *event_file = event_file_data(m->private);
 
-	if (t == SHOW_AVAILABLE_TRIGGERS)
+	if (t == SHOW_AVAILABLE_TRIGGERS) {
+		(*pos)++;
 		return NULL;
-
+	}
 	return seq_list_next(t, &event_file->triggers, pos);
 }
 
-- 
2.24.1